The present invention relates generally to the field of the treatment of aortic disease and in particular to endoluminal aortic stents and a method of deployment of such stents which allows accurate placement of a covered stent in the aorta. In particular it is capable of being deployed and positioned accurately above the renal arteries in the treatment of infra-renal aortic aneurysmal disease.
According to the prior art, aortic disease is often treated by surgical techniques involving the use of stents and grafts. For example, it is well known in the art to interpose, within the stenotic portion of an artery, a stent, whether made of stainless steel or other materials, capable of being balloon-expandable for strengthening the walls of a stenotic or occluded artery. In addition, it is well known in the prior art to use a graft to repair highly damaged portions of, for example, the aorta or other arteries thereby ensuring blood flow and reducing the risk of aneurisms or ruptures. The grafts, hollow tubes comprised of material such as dacron, are normally inserted within the walls of a damaged artery and can be sewn into position or expanded through the use of a stented balloon catheter.
A more severe problem occurs when it is necessary to use a graft at or around the intersection of a major artery (e.g. the aorta) with intersecting arteries (e.g. the renal arteries, carotid or brachycephalic artery). While the graft is clearly required to strengthen and ensure the flow of blood through, for example, the aorta, the use of a graft effectively seals or blocks off the blood flow to the kidneys or cerebral circulation. Accordingly, it is often impossible or impractical to use a graft to treat aortic disease at or around the intersection of the aorta and other arteries. Instead a surgeon must attempt to repair the weakened walls of such artery using other surgical techniques having high failure rates and limited success. For example, although several centers around the world have been routinely deploying endoluminal grafts for the treatment of infra-renal aortic aneurisms, as many as 30% of abdominal aortic aneurisms are unsuitable for this method of treatment due to an insufficient length of aneurysmal-free infra-renal aorta to firmly anchor the graft or stent.
The present invention solves the problem in the prior art by utilizing the supra-renal aorta to provide adequate anchorage for an aortic graft whilst at the same time employing extremely accurate placement of a fenestrated covered stent which corresponds to the exact sites of origin of the intersecting arteries.
The present invention in general relates to a fenestrated endoluminal aortic stent which is a single component device comprising two or more stainless steel or nitinol stents such as Z stents which may have caudally facing barbs sutured to a variable length of a bio-compatible material tube in which the stents are attached to the inside surface of the bio-compatible material tube and, depending on the geometry of the intersecting arteries to be covered, customized fenestrations accurately placed in the bio-compatible material tube corresponding to the intersecting artery openings.
In one form, therefore, the invention may be said to reside in a prosthesis comprising two or more stents sutured to a graft comprising a bio-compatible material tube, wherein the two or more stents are attached to the inside surface of the bio-compatible material tube and at least one fenestration in the bio-compatible material tube corresponding to an intersecting artery opening.
Preferably there are more than two stents attached to the bio-compatible material tube.
There may be a further stent fastened to the bio-compatible material tube and extending proximally from the bio-compatible material tube.
At least one of the stents may have caudally facing barbs thereon to assist with accurate retention of the prosthesis when completely inserted.
The proximally extending stent may be the stent which has the caudally facing barbs thereon.
The bio-compatible material tube may in one embodiment be a DACRON material tube.
There may be two or more fenestrations according to the number of intersecting arteries.
The or each fenestration may include one or more radiopaque markers defining a periphery of the fenestration.
The distal most of the stents may include a loop extending distally of the graft.
The prosthesis may further include a release mechanism for the prosthesis including one or more trigger wires wherein a portion of the bio-compatible material tube is folded longitudinally with the one or more trigger wires respectively threaded longitudinally through the bio-compatible material tube at the fold to retain the prosthesis in a partially compressed state.
At least one of the stents may include one or more shortened loops to enable location of the fenestrations as required.
Accurate siting of the branches of the aorta may be achieved from Computerised Axial Tomograms (CT) and angiography and the invention is customised to each patient in relation to the sites corresponding with the CT. The fenestrations are marked with radiopaque beads to facilitate their positioning under X-ray control before deployment.
In an alternative form the invention may be said to reside in a method for treating arterial disease at an intersection of two arteries, including the steps of:
X-raying arteries to be treated so as to accurately determine the position of the intersection of the arteries, customizing one or more fenestrations to a prosthesis comprising a selected length of a bio-compatible material tube, attaching radiopaque markers around the or each fenestrations, placing two or more stents into the bio-compatible material tube, bends in the stents being shortened if necessary in such a way so as not to cover the fenestrations, manually gathering a top stent, covering the top stent with a top cap and holding the stent in place in the top cap with a trigger wire, stitching the trigger wire or another trigger wire through a longitudinal fold in the bio-compatible material tube to narrow the diameter of said prosthesis thereby providing a customised fenestrated covered graft to be inserted into an artery to be treated.
The method may further include the step of sewing a further stent to the top ring of the bio-compatible material tube, such that the further stent extends proximally from the bio-compatible material tube.
There may be more than two stents attached to the bio-compatible material tube and two or more than two fenestrations according to the number of intersecting arteries.
The process of insertion of the graft may include the steps of; compressing the graft and placing it into a sheath which fits snugly around the top cap, the prosthesis, the stents and an obturator, inserting through a femoral artery in a groin the prosthesis using a delivery device which includes the top cap, the sheath, the obturator and guide wires, withdrawing the sheath to reveal the graft in semi-deployed position, positioning the prosthesis, partially withdrawing the sheath and obturator to enable insertion of angiography catheters and guide wires, inserting the angiography catheters and guide wires through a contralateral groin into the artery to be treated to provide maneuverability, and accurate positioning of the graft by positioning right and left angiography catheters and guide wires through the fenestrations into the intersecting arteries, releasing the trigger wire to provide full deployment of the the graft, withdrawing said angiography catheters and pushing up the sheath and obturator through the stent and docking with the top cap and fully withdrawing the delivery device, whereby the said fully deployed stent ensures the flow of blood at the intersection of the arteries to be treated.
The method by which the prosthesis of the present invention may be maneuvered into place prior to full deployment is by way of the right and left angiography catheters and guide wires.
The radiopaque markers may be gold or any other bio-compatible material which enables the marker to be visualized by X-ray or other methods.
This generally describes the invention but to assist with understanding of the invention reference will now be made to preferred embodiments of the invention with the assistance of the following drawings.